The Research Design of the following topic: Why do countries choose to challenge

The Research Design of the following topic:
Why do countries choose to challenge or cooperate with the declining hegemony?
The time period in this research is 1870-1914. My research design is a qualitative design using a comparative case study. My IVs (5 total) and DVs are included in the My Idea file.
The datasets that my professor suggested is called Militarized Interstate Dispute Dataset(free to download online), and Polity 5 Dataset, please feel free to pick other datasets.
It is easy to measure the DVs, but it is hard to measure the IVs (the professor said there is no variations in IVs, so it is maybe better to approach them from a more qualitative perspective)
I have attached the grading rubric, an research design example, article summary, literature review (associated readings), my idea on research design and relevant readings.
Please ask me if there are confusion, thank you so much.